The so-called polar modulation represents a method for generating a phase- and amplitude-modulated carrier signal. Here, the phase and/or the frequency of a high-frequency carrier is typically modulated via a respectively addressed PLL (phase-locked loop) and then additionally an amplitude modulation is imposed on the phase-modulated carrier by way of multiplication with a respective signal, as, for example, according to the following equation.RF(t)=A(t)·cos(2πf(t)+φ0)  (1)
In a polar modulator the input-side modulation information is separated into phase and amplitude information and processed separately. Polar modulators can be used in mobile radio devices, which are based on special modulation methods, for example, according to the mobile radio standard GSM-EDGE (Global System for Mobile Communication-Enhanced Data Rate for GSM Evolution) or UMTS.
In the past, in systems of conventional technology for polar modulators the clocks for the digital signal processing for the DAC in the amplitude path (Digital Analog Converter), the DCO, as well as the LO (local oscillator) channel frequency was generated from the VCO/DCO (Voltage/Digitally Controlled Oscillator) output frequency via separate particular divider circuits.